This invention relates generally to methods and systems for testing and more specifically to methods and systems for measuring electromagnetic emissions from electronic devices.
In the electronics industries, it is desirable to lessen electromagnetic emissions which may cause electromagnetic interference with other devices. Therefore, before an electronic device is sold in most parts of the world, the device is typically tested to determine levels of radiated and conducted emissions at various frequencies. A Programmable Logic Controller (xe2x80x9cPLCxe2x80x9d) product which cannot claim an industrial exemption is one example of an electronic device from which conducted and radiated emissions are measured. The emissions are measured in a range based on the highest frequency generated or used by the device or based on the highest frequency on which the device operates. Emissions from devices are measured to ensure compliance with regulations imposed by the United States Federal Communications Commission (FCC) and counterpart regulatory agencies in other countries.
It is well known that physical positions of various wires and cables connected to electronic devices can affect measured levels of radiation. For this reason, most regulatory agencies that address inadvertent electromagnetic radiation specify that wires and cables xe2x80x9cbe placed into positions that maximize field strength.xe2x80x9d
Practical experience reveals, however, that in a complex electronic device, there is no single position that results in maximum emissions at all frequencies. Rather, maximum emissions occur at different relative positioning of the device""s cables and wiring for each different frequency. Therefore it is desirable to find an optimal or xe2x80x9cbestxe2x80x9d cable and wiring positioning at each problem frequency for the device being tested.
Known emissions test systems suffer from two limitations. One limitation is that known systems are susceptible to human error because extensive operator intervention for equipment operation during an emissions scan is required. The second limitation is that typical known systems are incapable of computing a maximum quasi-peak value for optimally placed cables.
In an exemplary embodiment, an emissions measuring system minimizes human error factor by automating most of an emissions scan test procedure, including prompting a test engineer to perform cable manipulations at appropriate times during the testing procedure. In addition, data is recorded during the testing procedure while performing cable manipulations for complex electronic devices.
More particularly, the emissions measuring system performs a wide-band measurement of conducted and radiated emissions across a frequency spectrum of interest. The system also performs a narrow-band measurement of conducted and radiated emissions around select emissions resulting from the wide-band measurement. Additionally, the system determines a maximum quasi-peak value for optimal cable and wiring position from the narrow-band measurement, and communicates with a standard word-processing program to generate reports of measured emissions values, measured quasi-peak values and associated test conditions.